Ion Microscopy Imaging of Boron from p-Boronophenylalanine in Surgically Acquired Samples of Human Brain Tumor Tissue

Abstract

Using ion microscopy1 we are able to quantitatively image physiologically relevant isotopes, including ¹⁰B, in cancerous and contiguous normal tissues with cellular to subcellular resolution and with detection limits in the low-ppm to ppb range. Over the past several years we have been using this technique to analyze tissue sections from animal brain tumor models,1–3 as well as specimens prepared from tissue cultures,4,5 to develop appropriate cryogenic sampling procedures to be applied to the in situ analyses of ¹⁰B in human brain tumor specimens. An ion microscopy imaging study is presented which demonstrates the localization of ¹⁰B from the fructose complex of p-boronophenylalanine (BPA-F) in tumor cells from a patient with glioblastoma multi-forme. Patient A was infused intravenously for one hour to deliver 170mg BPA/kg body weight. The craniotomy commenced one-half hour after the end of the infusion. Tissue specimens from patient A were frozen on dry ice, stored at -80 °C, and at a later date cryosectioned and freeze-dried for ion microscopy analysis. The boron concentration in tumor cells, calculated from the grayscale intensity of ion images, was found to have a dynamic distribution with an average approximately 3.5 times higher than the ¹⁰B levels in the normal brain and blood. Ion images are shown to illustrate the complexities of cryogenic sample preparation for the analysis of ¹⁰B in human brain tumor tissues at the microscopic level.